I spoke on Friday with Rep. Adam B. Schiff (Calif.), the ranking Democrat on the House Intelligence Committee, and he stressed that we cannot be sure of the outlines of the arrangement they made.

But Schiff did suggest a few possible ways in which Manafort — who was convicted last month on tax and bank fraud charges and was facing more legal jeopardy — could shed light on questions involving a possible Trump campaign conspiracy with Russian interference in the 2016 election, or obstruction of justice.

First, Schiff noted, Mueller would likely want to know from Manafort as much as possible about the infamous June 2016 Trump Tower meeting, in which Donald Trump Jr., Jared Kushner and Manafort attended with the full expectation of getting dirt on Hillary Clinton supplied by the Russian government.

The congressman also noted that Mueller would want to know what Manafort can tell him about the “background to the Trump Tower meeting, what took place at the Trump Tower meeting, and what took place after the Trump Tower meeting.” It has not been established that Trump himself knew about this meeting at the time, but Manafort might be able to testify to that, as well.

On another conspiracy-related front, as Natasha Bertrand points out in the Atlantic, Manafort might be in a good position to shed light on what exactly former Trump campaign aide George Papadopoulos — who has testified as part of his own plea deal that he learned Russia had stolen information on Clinton in the form of “thousands of emails” — might have told campaign higher-ups about this at the time, another big unknown.

Schiff suggested that Manafort might also be able to shed light on any other illegal activity by the campaign. He pointed out that we did not learn that Trump had directed estranged personal lawyer Michael Cohen to make hush-money payments in violation of campaign-finance law until Cohen admitted it in court. There could be more such conduct that we haven’t learned about.

“There’s potentially a range of other illegal conduct that Manafort could shed light on, in much the way Michael Cohen did,” Schiff told me.

Schiff also pointed out that Manafort could conceivably open up about the joint-defense agreement he previously had with Trump, under which the two shared confidential information in a privileged setting.

“For months, as part of their joint defense agreement, they would have been strategizing together,” Schiff noted, adding that Manafort might be able to share information on “what conversations” Trump might have had with Manafort “after the charges were brought against him.” A long time has passed since Manafort was charged earlier this year. What have Trump and Manafort discussed about this during the interim?

Which leads to questions about a possible pardon for Manafort. “If the president or his team were dangling a pardon in conversations with Manafort, that would go to the issue of obstruction of justice as well,” Schiff said. And Manafort could conceivably fill Mueller in on that, if it happened.

Back in August, after Cohen pleaded guilty, Trump praised Manafort for refusing to “break,” suggesting that Manafort holding strong was very much in his interest. Now that Manafort has indeed “broken,” Trump has yet to issue a tweet.

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Greg SargentGreg Sargent writes The Plum Line blog, a reported opinion blog with a liberal slant — what you might call “opinionated reporting” from the left. Follow